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[accessories box] [power cord] [audio patch cord] [lumbar cushion] [headphones] [keying devices] [power supply] [FF33 field-telephone] [re-inking device]
The accessories of the Hell Feldfernschreiber are stored on the inside of the lid of the carrying case:
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an accessories box, containing:
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a 2 m long power cord, for connecting the machine to a source of 12 volt DC. |
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a 1.2 m long audio patch cord, to connect the electronics box to a radio receiver. |
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a 1 page operating manual. |
Inside of the lid of a Feld-Hell carrying case - complete with power cord and accessories box
(patch cord for connecting to radio receiver
not shown)
ACCESSORIES BOX
Top of Feld-Hell accessories box
Top of Feld-Hell accessories box
(re-labeled for the Italian "market")
Accessories box and its contents
(box and ink bottle were re-labeled for the
Italian "market")
The Hellschreiber ink roller and spare felt rings
Original small box
with spare ink roller
(photo courtesy John Alexander Wilson)
An original ink
bottle
(photo courtesy John Alexander Wilson)
The 1941 Feld-Hell manual recommends using ink ("Schreibfarbe") that is a "colloidal solution of pigment in oil". This minimizes drying out of the felt roller and collecting deposits of ink on the spindle. The same manual prescribes the use of special ink "HB 45 violett".
Original cardboard strip with spare carbon brushes for the motor and drum
Original cardboard strip with spare fuses, carbon brushes for the generator, and
lamp
POWER CORD
The electronics box of the Feld-Hell is connected to a 12 volt power source with a 2 m long power cord. This can be a 12 volt car battery, or a 12 volt power supply.
The power cord
The original 12 Vdc plug that came with my Hellschreiber
AUDIO PATCH CORD
For operation via radio, the "Empfänger" (receiver) connector of the Feld-Hell's electronics box is hooked up to the headphones output of a radio receiver, with an audio patch cord.
Audio patch cable
for hooking up to the loudspeaker / headset output of a radio receiver
(note the white polarity dot near one of the prongs on each plug)
LUMBAR CUSHION
Hauling a 25 kg piece of equipment on your back is no joy. To help ease the pain, the "Tornister" carrying case of the Feld-Hell has two tracks for inserting a cushion.
Lumbar cushion ("Rückenpolster") for the back pack carrying-case ("Tornister ")
Soldier with a "Tornister" (here: a radio, not a
Hellschreiber) strapped to his back
Two more "Tornister" radios with a cushion
HEADPHONES
The "Mithören" (monitoring) output of the Feld-Hell is for hooking up a standard 4000 ohm headset. I use a Dfh.a "Doppelfernhörer" (thank you Rolf!). This is a common set of double headphones, with two 2000 ohm "ears" in series - typical for headsets of the era. Per the 1941 manual (ref. 2), the headset gives better sound quality than a field telephone, and is also used for monitoring the own-station's Morse telegraphy signals (when using the Morse key of the keyboard).
My 1943 headset type Dfh.a
My headset came with household zip-wire cord. I replaced it with very flexible cloth-covered tinsel wire (which is near impossible to solder). I'm still trying to locate original double-plugs. Over the years, the magnets in the ear pieces tend to lose their strength, hence, volume of the sound. They can be re-magnetized with a strong permanent magnet, or an electro-magnet. Ref. 5, 6.
(source: Popular Science, Vol. 137, No. 4, October 1940, p. 169)
KEYING DEVICES
When inserting a plug into the 12-pin round connector on the Feld-Hell's electronics box, the contacts of the character drum (and Morse key) are diverted to this connector. They can be used for direct keying a CW transmitter. Do not apply more that 200 volt to these contacts, and draw no more than a couple of milli-amps through them (2 watts max combined); ref. 7 (1942) actually suggests limits of 0.1 mA and 100 volt (1 watt max combined).
Direct keying of a CW transmitter is no problem with solid-state CW transmitters or tube transmitters with a solid-state keying relay. However, older tube transmitters may have significant negative or positive voltage at the key input connector. This depends on whether grid (grid-block) keying, cathode keying, or anode keying is used. Key-down current draw may also be significant. This may exceed the voltage, current and power limits of the Hellschreiber's character drum and slip contacts. Rudolf Hell and his co-workers (ref. 8, 9) recommend such direct keying only for low power tube transmitters. For medium power (up to 100 W) they describe a keying device (a "Tastgerät") between the drum contacts and the transmitter's key input. The circuit takes the continuous 900 Hz tone of the Hellschreiber (available at the 12-pin round connector of the Feldfernschreiber), transforms its 2 Vpp up to 400 Vpp, and uses a rectifier tube to rectify this continuous tone. Ripple smoothing is done with a simple RC-filter. The resulting voltage is passed through a large current-limiting resistor (1 MΩ) to the key input of a grid-keyed transmitter. The Hellschreiber's drum contacts (also available at the 12-pin connector) are connected across that key input. They short the key input when pixels are transmitted. Anode and filament heater power for the rectifier tube is also available at the 12-pin connector.
Feld-Hell
"Relaistastgerät" (relay-based transmitter keying-device)
(source: fig. 26 in ref. 1)
POWER-SUPPLY
Besides a 12 volt battery, the Feld-Hell can also be powered by a 12 volt transformer-rectifier unit such as the standard "Gleichrichter" shown below.
Early models of these power supplies had poor power regulation, especially under low load conditions. This is why there is a switch on top of the electronics box of (most) Feld-Hells. It switches in a series resistor with the 12 volt power input, to avoid over-voltage conditions when the Feld-Hell is in the stand-by ("Bereit") mode.
A Wehrmacht "Gleichrichter"
transformer-rectifier unit that could be used with the Feld-Hell
(the marking "Ark" at the top right-hand corner
means that the equipment was OK for arctic use)
THE FF33 FELDFERNSCHREIBER
For operation over phone -lines, line item 72 of the 1941 manual (ref. 2) prescribes that a Feldfernsprecher (field telephone) be connected to the Feld-Hell's electronics box. It is used to call the opposite station. One end of a phone patch cord is plugged into the La-Lb/E jack of the Feld-Hell, the other end is plugged into the side of an FF33 Feldfernsprecher telephone set. Ref. 3 and 10 provide a good overview of this standard telephone set.
Set-up of the Feld-Hell for operation over phone lines
(source: Appendix 2 of ref. 2)
As the designator "33" suggests, the FF-33 was developed in 1933; it entered service in 1934 with the Reichswehr and Reichspost. The FF-33 was built until the end of WWII. It continued to be used with the Bundespost and Bundeswehr until well into the 1970s! Compared to its 1926 predecessor, the FF-26, it has a case made of molded bakelite, rather than a wooden case. The FF-33 is equivalent to the American EE-8 field telephone (in service until well after the Vietnam war).
An FF33 Feldfernsprecher
(the color of the bakelite case of the FF33 varies from bright brown to near-black dark brown)
"Vermittlungsschnur" - phone patch cord
(plugs into the phone jack of the Feld-Hell and in the side of the FF33 field telephone)
Plug ("Stöpsel") for the La-Lb/E phone line jack
RE-INKING DEVICE
Decades after introduction of the Feld-Hell, the Hell company developed and marketed a re-inking device or ink-applicator ("Einfärbvorrichtung"). This to put an end to the rather messy manual process of re-inking the felt rolls. In October of 2009, I bought one of these gadgets via eBay for a mere €4.50 (≈$6.75). It is NOS ("new old stock"); mine was manufactured in 1970. Cf. ref. 3 for the users manual.
"Einfärbvorrichtung"
re-inking device for Hellschreiber felt ink rollers
Original label on the packaging of the re-inking device
REFERENCES
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Ref. 1: "Stand der Siemens-Hell-Fernschreibtechnik", Rudolf Zimmerman, Siemens & Halske A.G. - Wernerwerk, Technische Mitteilungen des Fernmeldewerks, Abteilung für Telegrafengerät, SH 7997. 0,5. 1043. TT1. M/1401, May 1940, 10 pp. (courtesy Siemens Corporate Archives, München) |
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Ref. 2: "Der Feldfernschreiber", document D 758/1 of the Oberkommando des Heeres, Heereswaffenamt, Amtsgruppe für Entwicklung und Prüfung, Berlin, 1 April 1941; this is the official original manual in German for model T typ 58 (a.k.a. model 24a-32, a1, a2, based on drawing numbers).
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Ref. 3: "German Field Line Communication equipment of WW2", Funksammler Publ., 2010, 147 pp. [17 MB] |
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Ref. 4: "Einfärbvorrichtung Type EF 2/B - Gebrauchsanleitung" [instructions for using the re-inking device], 1 p. (courtesy Heinz Blumberg, DC4GL) |
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Ref. 5: "Einfaches Verfahren zum Aufmagnetisieren alter Kopfhörer" [simple process for re-magnetizing old headphones], Helmut Kern, Funkgeschichte (Gesellschaft der Freunde der Geschichte des Funkwesens e.V.), Heft 130, 2000, pp. 82-83 See note 1. |
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Ref. 6: "How to Rejuvenate your Headphones", Tom Provost, Gary D'Amico, presented at the November 1996 Meeting of the New Jersey Antique Radio Club (NJARC) |
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Ref. 7: "Siemens-Hell-Schreiber", pp. 149-166 in “Fernmeldetechnik“, Band 9 of “Lehrbücher der Feinwerktechnik“, Fritz Schiweck, 1st ed., 1942, 526 pp., C. F. Winter'sche Verlagsbuchandlung |
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Ref. 8: section 9a and 9b in "Die Entwicklung des Hell-Schreibers" by the inventor himself: Rudolf Hell; pp. 2-11 in "Gerätentwicklungen aus den Jahren 1929-1939", Hell - Technische Mitteilungen der Firma Dr.-Ing. Rudolf Hell, Nr. 1, May 1940 [in German] |
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Ref. 9: section 4a in "Der Siemens-Hell-Feldschreiber", by Rudolf Hell's co-workers G. Ege and H. Promnitz, pp. 11-20 in "Gerätentwicklungen aus den Jahren 1929-1939", Hell - Technische Mitteilungen der Firma Dr.-Ing. Rudolf Hell, Nr. 1, May1940 [in German] |
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Ref. 10: "German Field Telephone Equipment Reference - Feldfernsprecher 33 / Field Telephone 33", Karl-Heinz Kümmer |
Note 1: I have this document on file, but can not post it here, due to copyright reasons.
©2008-2010 F. Dörenberg N4SPP
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